There are concerns that any activities involving a naked flame could set off another blaze in the grass which has become tinder try in the recent hot weather.
The moorland blaze, which started as two separate fires which then combined around three weeks ago, took a huge effort to bring under control, involving forces from across the North West.
In shocking scenes rarely seen in the UK, the flames and thick plumes of smoke were visible for miles.
Firefighters are still treating part of the area, whose total reach stretches from Chorley to Bolton, as an ongoing incident which is gradually being wound down.
Various road closures are still in place.
A Lancashire Fire and Rescue statement said: “We’ve just had reports of walkers up at #WinterHill and people with disposable BBQ’s.
“We still have crews working at this incident so please help us by taking note of the exclusion zone still in place and not having BBQs in this dry environment.”
With more fine weather to come over the next few days and into the weekend, Bolton Mountain Rescue Team has provided Lancashire Fire and Rescue Service with map showing the areas that have been affected by the fire and where we need people to stay away from.
A spokesman for the fire service said: “The red area is a fire ground. This cordon is not only for public safety but it will ensure that you don’t get in the way of emergency responders, to enable them to maintain the progress we’ve made so far.
“It will also help us return full access to the area to you as soon as possible.”
Visitors to the site are also being urged to abide by road closures.